Introduction: In the last decades, the great technological development increased Internet popularity, emerging the concern about its overuse. The objectives of this study were to assess and characterize Internet use in adolescence, determine Internet addiction and clarify its association with sleep disorders and excessive daytime sleepiness.Material and Methods: It was performed an observational, cross sectional and community-based study. The target were students attending 7th and 8th grades, to whom was applied an online self-report questionnaire to assess sociodemographic features, Internet use, Internet dependence, sleep characteristics and excessive daytime sleepiness.Results: A total of 727 adolescents were included with a mean age 13 ± 0.9 years. Three-quarters of teenagers use Internet daily and 41% do it for three or more hours/day, mainly at home. The phone and laptop were the main devices used. Online games and social networks use were the main activities performed. Internet dependence was observed in 19% of adolescents, and it was associated with male gender, social networks use, mainly Twitter and Instagram use, self-perceived sleep problems, initial and middle insomnia and excessive daytime sleepiness (p < 0.05).Discussion: The results confirm the highlight that Internet has in adolescents routine, who prioritize in their use access to social networks and online games, using single devices, less subject to parental control.Conclusion: The Internet addiction rate observed and its association with sleep alterations and daytime sleepiness emphasizes the importance of this issue.